The 50 most recently published documents
We study the impact of underdamped intramolecular vibrational modes on the efficiency of the excitation energy transfer in a dimer in which each state is coupled to its own underdamped vibrational mode and, in addition, to a continuous background of environmental modes. For this, we use the numerically exact hierarchy equation of motion approach. We determine the quantum yield and the transfer time in dependence of the vibronic coupling strength, and in dependence of the damping of the incoherent background. Moreover, we tune the vibrational frequencies out of resonance with the excitonic energy gap. We show that the quantum yield is enhanced by up to 10% when the vibrational frequency of the donor is larger than at the acceptor. The vibronic energy eigenstates of the acceptor acquire then an increased density of states, which leads to a higher occupation probability of the acceptor in thermal equilibrium. We can conclude that an underdamped vibrational mode which is weakly coupled to the dimer fuels a faster transfer of excitation energy, illustrating that long-lived vibrations can, in principle, enhance energy transfer, without involving long-lived electronic coherence.
Synergien
(2020)
BGH, 24.01.2020 - V ZR 155/18: Gewohnheitsrecht kann im Einzelfall kein Notwegerecht begründen
(2020)
Nerzzucht mit Hindernissen – oder: alle juristischen Auslegungskriterien plus Analogie in einem Fall
(2020)
Einige Städte im Ruhrgebiet haben die vielfältigen Herausforderungen im Umwelt-, Klima-, Mobilitäts-, Wirtschafts- und Bildungsbereich mit ganzheitlichen Strategien, die z.T. an den Nachhaltigkeitszielen der UN orientiert sind angegangen. Es werden einige ausgewählte Städte in ihren Zielsetzungen, organisatorischen Strukturen und Handlungsfeldern betrachtet und erfolgreiche Faktoren herausgestellt.
Allgemeines Verwaltungsrecht
(2020)
Juristische Methodenlehre
(2020)
Die Digitalisierung bietet Kommunen und Unternehmen neue Gestaltungsmöglichkeiten im Hinblick auf die Prozesse der Daseinsvorsorge. In dieser Arbeit wird ein Fokus auf die Müllentsorgung gelegt. Basierend auf der Übertragungstechnologie "LoRaWAN" soll mithilfe von Algorithmen ein Konzept ausgearbeitet werden, dass die Müllentsorgung erleichtert.
Im Vorfeld wird geprüft, welche Konzepte andere Städte bereits vorweisen, um dann im Anschluss ein Konzept für die Stadt Gelsenkirchen zu entwickeln. Unter Verwendung der Graphentheorie sollen die kürzesten Wege gefunden werden, um diese mit Methoden der Statistik zu erweitern. Dies soll eine Möglichkeit bieten, bereits im Vorfeld Prognosen über Füllstände zu ermöglichen.
The activated sludge respiration inhibition test and the luminescent bacteria test with Vibrio fischeri are important bacterial test systems for evaluation of the toxicity of chemical compounds. These test systems were further optimized to result in better handling, reliability and sensitivity. Concerning the Vibrio fischeri test, media components such as yeast extract and bivalent cation concentrations like Ca2+ and Mg2+ were optimized. The cultivation, storage conditions and reactivation process of the stored bacteria were also improved, which enabled simpler handling and led to good reproducibility. Additionally, the respiration inhibition test with a prolonged incubation time was further analyzed using different chlorinated phenols as reference compounds. It could be stated that a longer incubation period significantly improved the sensitivity of the test system.
Stereotactic frame systems are widely used in neurosurgery. The accuracy of frame devices is considered as a gold standard to which the accuracy of new frameless stereotactic navigation systems is compared. The purpose of this study is to develop a general approach for the prediction of the application accuracy of stereotactic systems. The approach will be applied to the frame‐based biopsy performed with three frame devices: Leksell G, Cosman–Roberts–Wells (CRW), and Brown–Roberts–Wells (BRW). A work‐flow analysis will be carried out demonstrating that the accuracy relevant for a clinical application comprises several error sources including imaging, target and entry point selection, image to frame coordinates registration, and the setting of mechanical parameters of the frame. These error sources will be postulated to obey a Gaussian distribution probability density. The linear, i.e., Gaussian, error propagation, will be used to link all error contributions thus to calculate the cumulative accuracy of the frame used in the application. Although the Gaussian approach is an approximation, it allows for an analytical treatment of the accuracy. Both the accuracy at the target point and the accuracy of the probe needle guidance along the planned trajectory have been investigated. Of great significance is the relationship found between accuracy, pixel dimension, and image slice thickness, the latter being the dominant factor for slices of more than 1.5 mm thickness, yielding inaccuracies larger than 1.5 mm. For target points the predictions for the application accuracy have been compared to the results of measurements, showing good agreement with the experimental data.
Three-dimensional magnetic resonance medical images may contain scanner- and patient-induced geometric distortion. For qualitative diagnosis, geometric errors of a few millimeters are often tolerated. However, quantitative applications such as image-guided neurosurgery and radiotherapy can require an accuracy of a millimeter or better. We have developed a method to accurately measure scanner-induced geometric distortion and to correct the MR images for this type of distortion. The method involves a number of steps. First, a specially designed phantom is scanned that contains a large number of reference structures on positions with a manufacturing error of less than 0.05 mm. Next, the positions of the reference structures are automatically detected in the scanned images and a higher-order polynomial distortion-correction transformation is estimated. Then the patient is scanned and the transformation is applied to correct the patient images for the detected distortion. The distortion-correction method is explained in detail in this paper. The accuracy of the method has been measured with synthetically generated phantom scans that contain an exactly-known amount and type of distortion. The reproducibility of the method has been measured by applying it to a series of consecutive phantom scans. Validation results are briefly described in this paper, a more-detailed description is given in another submission to SPIE Medical Imaging 2001.
